Signal gating circuit and vehicle starting control circuit



June 20, 1967 R. D. SMiTH 3,327,138

SIGNAL GATING CIRCUIT AND VEHICLE STARTING CONTROL CIRCUIT Filed Aug.21, 1964 K To ()ufpuf Circuif l/V'VE/V TOR. ROBERT 0. 554/ TH yW/M I A Iforneys United States Patent 3,327,138 SIGNAL GATING CIRCUIT AND VEHICLESTARTING CONTROL CIRCUIT Robert D. Smith, Turtle Creek, Pa., assignor ofone-half to Donald Heaton, Verona, Pa. Filed Aug. 21, 1964, Ser. No.391,156 9 Claims. (Cl. 30788.5)

This invention relates to an improved signal gating circuit and moreparticularly to such a circuit for use as a motor vehicle startingcontrol circuit.

Gating circuits have a wide variety of uses where only selected signalsare desired to be passed to another circuit. While gatecircuits are notnew per se, the present invention provides a unique time delay circuitfor selectively passing a signal to an output circuit.

According to the invention a first input signal initiates a first timedelay t of indeterminate duration after which time a second delay I isstarted and a feedback signal is generated. The latter signal signifiesthe start of the second time delay t of predetermined duration andsignals the acceptability of a second input signal during a gateinterval t after expiration of t but before expiration of t Expirationof the second time delay, absent the re-' ceipt of the second inputsignal, blocks or inhibits passage of the second input signal to anoutput circuit. Receipt of the second input signal before or after thegate interval z also blocks or inhibits passage of the second inputsignal to the output circuit. Stated differently, the circuit is suchthat the desired passage of a second input signal to an output circuitis possible only after receipt of a first signal and after theexpiration of a first time delay but before expiration of a second timedelay.

While the circuit herein is useful in numerous applications, thedescription hereafter will be largely addressed to one embodiment of theinvention in a motor vehicle starting control circuit. Where the inputsignals referred to above are signals actuated by a vehicle operator andthe output circuit is the motor vehicle starting circuitry, the deviceaffords a means for inhibiting operation of the vehicle by an individualwho cannot react to a stimulus within a predetermined time interval. Thereaction times referred to are the minimum times for a human operator toproduce a simple, non-choice response to a stimulus. in the particularapplication herein, the times refer to the minimum reaction time for anoperator 'to turn an ignition key in response to a stimulus. Using a keyignition switch having an ON position and a momentary START position,corresponding to the firstand second input signals, it is apparent thatthe operator must successfully follow the sequence earlier described inorder to start the vehicle. Thus, the ignition must first be switched tothe ON position to initiate the indeterminate time delay t after whichthe operator is signaled to switch to the START position. The operatormust respond to this signal Within the gate interval 1 to successfullyactuate the starting circuitry. Failure to respond within the gateinterval requires the operator to reinitiate the entire sequence. Aswill later be described more fully, attempts to preempt or out-guess thedevice are frustrated by the circu-it arrangement. The time delays andsequence of operation are chosen so as not to unduly burden an operatorwhose reaction times have not been impaired to the extent that they riseabove a predetermined level, but at the same time present a test whichcannot .be readily performed by a person whose ability to react has beenso impaired.

An object of the present invention is to provide a new and useful signalgating circuit.

Another object is to provide a novel vehicle starting control circuit.

A further object is to provide such a circuit as will inhibit vehicleoperation by an individual whose reaction times rise above apredetermined level.

These and other objects will be apparent to those skilled in the art andmore readily understood by reference to the following description,wherein:

FIG. 1 is a schematic illustration of the circuit of the invention; and

FIG. 2 is a diagrammatic illustration of the relationship between thevarious time delays.

Referring to the drawing, one embodiment of the invention isillustrated. Power Supply 2 is the vehicle battery connected betweenterminals A and C (ground) and provides the power for operating theremaining components. Switch 3 is a standard type of double pole vehiclekey ignition switch shown in OFF position, and has two active positions,ON and START. In the ON position, one pole 3a of the switch contactsterminal A; in the START position, the other pole 3b contacts terminal Bwhile pole 3a maintains contact with terminal A, the latter terminalhaving junction points 4, 5, 6 and 7. A time delay relay 8 is connectedat 4 across the terminals A and C and has normally open contacts 8aconnected in series between 4 and 5 of terminal A and in parallel withrelay 8, which is a thermal delay device selected so as to provide adelay time of approximately 1-10 seconds before closing the contacts 4a.

A relay 9, having contacts 9a in series with terminal B, is connected atone end to terminal A at 5 through a current limiting resistance havinga positive temperature coefiicient such as a tungsten lamp 10, the otherside of relay 9 being connected to terminal C. In parallel with relay 9,there is a silicon gate rectifier 11 having its anode connected to Athrough the lamp 10 and its cathode connected to C.

Between point 6 of terminal A and terminal C, there is connected auni-junction transistor 12 having its basetwo region connected to Athrough resistor 13 and its base-one region connected to C throughresistor 14 and also to the gate of rectifier 11. The emitter oftransistor 1'2 is connected to A through a variable resistor 15, and isconnected to C through capacitor 16 which is preferably an electrolyticcapacitor exhibiting good stability despite variations in ambienttemperatures, such as a tantalum capacitor. The RC time constant ofresistor 15 and capacitor 16 is preferably adjustable through a range offrom 200 to 500 milliseconds. The emitter of transistor 12 is furtherconnected to the anode of diode 17 whose cathode is connected to A, at7, through resistor 18 and also to the anode of silicon gate rectifier'19. The cathode of rectifier 19 is connected to A through a resistancehaving a positive temperature coeflicient such as tungsten lamp 20, andis also connected to C through resistor 21. The gate of rectifier 19 isconnected to C through resistor 22. Across terminals B and C, there aretwo series resistors 23 and 24 having their junction 25 connected to Cthrough capacitor 26 and diode 27' whose cathode is connected to Cthrough resistor 22.

Operation is equal to the indeterminate time delay of relay 8.

, the output circuit and is equal to t less the time 1 re- Interval t isthe precise time delay required to charge capacitor 16 to the firingpotential of transistor 12. Interval t is that portion of t during whichrectifier 19 must be gated to successfully pass a START signal to quiredto heat the filament of bulb 20.

When switch 3 is placed in the ON position, thermal relay 8 is energizedand closes contacts 8a after an indeterminate time delay. Closing ofcontacts 801 energizes relay 9 which immediately closes contacts 9a.Contacts 9a are physically located adjacent the ignition switch so thattheir closing produces a tactile feedback signal to the operatorindicative of the expiration of the first delay t Other feedbacksignals, such as visual or aural signals, are possible by providingadditional contacts on relays 8 or 9, for example, to actuate varioustypes of indicators (not shown) as will be readily understood by thoseskilled in the art. Closing contacts 8a commences the charging ofcapacitor 16 through resistance 15 to initiate time delay t ofapproximately 300 milliseconds duration, and passes current through bulb20 to commence a time delay t running concurrently with the time delay 1When sufiicient time has elapsed to charge capacitor 16 to a potentialsufiicient to drive transistor 12 into conduction, a pulse appearsacross baseone resistance 14 to fire or gate the rectifier 11 drivingthe latter into conduction. When rectifier 11 conducts, relay 9 iseifectively short-circuited, resulting in opening of contacts 9a todisable passage of a START signal to the output circuit. The circuit isthen said to be in a NO-GO configuration.

On the other hand, if switch 3 is turned to the START position duringthe interval t rectifier 19 will be gated, thereby clamping the emitterof transistor 12 to a level insufiicient to produce a gate for rectifier11. The explanation for this is that when contacts 8a close, diode 17 isreverse biased with a substantial positive voltage on its cathode, whichvoltage is greatly reduced when rectifier 19 is gated by the potentialdeveloped across resistor 22 when the switch 3 is placed in STARTposition. Gating of rectifier 19 effectively provides a short circuitacross capacitor 16 so the latter cannot charge to a voltage suflicientto drive unijunction transistor 12 into conduction to produce a gatepulse to fire rectifier 11. Thus contacts 9a remain closed and thecircuit is said to be in a G configuration.

The operator is prevented from pre-empting the device because of thecircuitry associated with the gating of rectifier 19. One obvious methodof attempting to circumvent the safety features would be to simply turnswitch 3 to the START position and hold it there while the first timedelay runs out in the expectation of immediately gating rectifier 19.Such an attempt will not be successful as will now be explained. Withthe contacts 8a open and the switch 3 in START position, capacitor 26will begin to charge through resistor 22 and diode 27. The charging timeis made quite short and is determined by the size of the capacitor 26,resistors 22 and 23 and the forward resistance of diode 27 which areselected to provide a short RC time constant on the order of 1millisecond, the total charge time being approximately milliseconds.Thus, the capacitor 26 would be rapidly charged so no gating pulse couldbe developed across resistor 22 to gate rectifier 19 when t expires.

Bulb 20 also serves to frustrate guessing by providing a time delay I;.;(equal to t t of approximately 200 milliseconds after the closing ofcontacts 8a, during which time rectifier 19 may not be gated; Theresistance of bulb 20 and resistor 21 form a voltage divider for biasingthe cathode of rectifier 19. The cold resistance of bulb 20(approximately 3 ohms) is such that the cathode of rectifier 19 isbiased by the potential across resistor 21 with a sufficiently largepositive potential to prevent gating the rectifier even if a gatingpulse is present. This biasing potential decays as the filament of bulb20 heats to a resistance of approximately 45 ohms leaving only a smallpositive potential on the rectifier cathode thereby enabling a pulsedeveloped across resistor 22 to gate rectifier 19. The time delayinherent in bulb 20 will not penalize the ordinary operator since thattime has been found to be less than the minimum reaction time for mostpersons to respond to the signal received on closing of contacts 9a,thus only those who do not follow the prescribed sequence will behampered by this delay.

A first unsuccessful attempt togate rectifier 19 will prevent immediaterepeated attempts because of the long discharge time of capacitor 26. Ashas been already shown, no gate pulse can be developed when capacitor 26is charged, and an unsuccessful attempt results in charging capacitor26. This charge is removed only by the discharge of the capacitorthrough the high backward resistance of diode 27 and resistors 22 and24. Alternatively, a high discharge resistance 28, shown in dottedlines, may be provided across the capacitor 26. The unsuccessfuloperator must therefore, wait for the capacitor to discharge, which maybe about five seconds, before reinitiating the sequence. The switch 3must be turned to the full OFF position to reinitiate the sequence inorder at reset the now-conducting rectifier 11 to a non-conducting stateby removing the anode voltage.

The rectifiers 19 and 11 together form a bi-stable state such that wheneither is gated before the other the circuit is locked in a G0 or NOGOconfiguration, respectively.

Once rectifier 19 is gated before rectifier 11, the operat-or maycontinue to switch back and forth between the ON and START positions topass the START signal to the output circuit since the rectifier willcontinue to conduct and contacts 8a and 9a will remain closed.

The circuit herein described is not intended to be limited to theparticular components shown in the embodiment nor to the particularapplication set forth. As will be obvious to those skilled in the art,numerous modifications and applications are possible within the scopeand spirit of the invention disclosed.

I claim:

1. In a control circuit having input and output circuits and means forsequentially applying first and second input signals, the second inputsignal being applied after application of the first signal but duringthe duration of the first signal, a signal gating circuit comprising:

(a) first and second time delay means, the first delay means beingactuated by the first input signal,

(b) means responsive to the expiration of the first time delay foractuating the second delay means, and

(c) gate means responsive to the first and second input signals and incircuit with the delay means for passing the second input signal to theoutput circuit only during the interval of the second time delay.

2. The circuit defined in claim 1, wherein the gate means comprises,

(a) first and second switching means, the first switching meansinhibiting passage of the second signal to the output circuit whenactuated, the second switching means being actuated by the second signalwhen the latter is received during the second delay interval, theactuation of the second switching means inhibiting actuation of thefirst switching means for permitting the passage of the second signal tothe output circuit, and

(b) means actuating the first switching means on expiration of thesecond time delay interval.

3. The circuit defined in claim 2, wherein the first and secondswitching means are semi-conductor gate rectifiers and wherein the meansactuating the first switching means comprises a uni-junction transistorhaving its output electrode connected to the gate of the first switchingmeans and being connected so as to produce a gating pulse on the outputelectrode when the second delay interval expires.

4. The circuit defined in claim 1, including a third time delay meansactuated by the means responsive to the expiration of the first timedelay, for producing a time delay interval shorter than the seconddelay, and wherein the gate means passes the second input signal to theoutput circuit only during that portion of the second interval whichextends beyond the third interval. 5. A vehicle starting control circuithaving a power supply and an output starting circuit, comprising,

(a) an ignition switch having ON and START positions and being soarranged that when the switch is in the START position the switchremains also in its ON position,

(b) means in circuit with the switch for connecting and disconnectingthe power supply to and from the output circuit through the STARTposition, representing GO and NO-GO configurations respectively,

(c) first time delay means connected to be actuated when the switch isin ON position,

((1) second time delay means in circuit with the first delay means andconnected to be actuated on expiration of the first delay, and

(e) bi-stable gate means in circuit with the switch and the first andsecond delay means for locking the circuit in the GO configuration whenthe switch is placed in START position during the interval of the seconddelay and for locking the circuit in the NO-GO configuration when theswitch is positioned to its START position during an interval other thanthat of the second delay.

6. A vehicle starting control circuit having a power supply and anoutput starting circuit, comprising,

(a) an ignition switch having ON and START positions,

(b) means in circuit with the switch for connecting and disconnectingthe power supply to and from the output circuit through the STARTposition, representing GO and NO-GO configurations respectively,

(c) first time delay means connected to be actuated when the switch isin ON position,

(d) second and third time delay means in circuit with the first delaymeans and connected to be actuated on expiration of the first delay, thethird delay interval being shorter than that of the second, thedifference between the second and third delay intervals beirig a gateinterval, and

(e) bi-stable gate means in circuit with the delay means for locking thecircuit in the GO configuration when the switch is placed in STARTposition during the gate interval and for locking the circuit in theNOGO configuration when the switch is turned to the START position otherthan during the gate interval.

7. The circuit as defined in claim 6 including means responsive to theexpiration of the first time delay for generating a feedback signal forindicating to a vehicle operator the expiration of the first delay.

8. The circuit as defined in claim 7 wherein the first delay means is athermal delay device having an indeterminate belay time, the seconddelay means comprises a series connected resistance and capacitance, andthe third delay means is a resistance having a positive temperaturecoefiicient.

9. The device as defined in claim 8, wherein the bistable gate meanscomprises a uni-junction transistor having its emitter connected to thejunction of the resistance and capacitance for roducing a pulse at theexpiration of the second time delay, first electronic switching meansconnected to receive the pulse to lock the circuit in the NO-GOconfiguration, and second electronic switching means connected to beactuated when the ignition switch is turned to the START position duringthe gate interval for locking the circuit in a G0 configuration.

References Cited UNITED STATES PATENTS 3,158,758 11/1964 Pearson 30788.53,206,612 9/1965 Swanekamp et a1. 307-885 3,253,157 5/1966 Lemon 30788.53,267,382 8/1966 Adem 32872 ARTHUR GAUSS, Primary Examiner.

B. P. DAVIS, Assistant Examiner.

1. IN A CONTROL CIRCUIT HAVING INPUT AND OUTPUT CIRCUITS AND MEANS FORSEQUENTIALLY APPLYING FIRST AND SECOND INPUT SIGNALS, THE SECOND INPUTSIGNAL BEING APPLIED AFTER APPLICATION OF THE FIRST SIGNAL BUT DURINGTHE DURATION OF THE FIRST SIGNAL, A SIGNAL GATING CIRCUIT COMPRISING:(A) FIRST AND SECOND TIME DELAY MEANS, THE FIRST DELAY MEANS BEINGACTUATED BY THE FIRST INPUT SIGNAL, (B) MEANS RESPONSIVE TO THEEXPIRATION OF THE FIRST TIME DELAY FOR ACTUATING THE SECOND DELAY MEANS,AND (C) GATE MEANS RESPONSIVE TO THE FIRST AND SECOND INPUT SIGNALS ANDIN CIRCUIT WITH THE DELAY MEANS FOR PASSING THE SECOND INPUT SIGNAL TOTHE OUTPUT CIRCUIT ONLY DURING THE INTERVAL OF THE SECOND TIME DELAY.